The present invention relates to a technique for forming a liquid film by supplying a liquid onto a substrate to be processed, and more specifically, to an apparatus and method of selectively forming the liquid film on the substrate.
In a manufacturing step of the semiconductor device, a liquid such as a resist or an SOG (Spin on Glass) solution is coated on a substrate. In a spin-coating method which has been conventionally used in a lithographic process to coat the liquid on the substrate, almost all amount of the liquid supplied onto the substrate is discarded out of the substrate and the remainder (several %) held on the substrate is used in forming a film. Therefore, a large amount of the liquid (such as a chemical agent) is wasted. Furthermore, a large amount of the chemical agent is released outside, negatively affecting the environment. In the case where a rectangular substrate or a large-aperture disk-form substrate (12 inches or more) is used, a turbulence is generated around the substrate, with the result that the obtained film is not uniform at outer peripheral portion thereof.
As a method of coating the chemical agent uniformly over the main surface of a substrate while the chemical agent is not wasted, Japanese Patent Application KOKAI Publication No. 2-220428 discloses a method of forming a uniform film by supplying a resist from a plurality of nozzles arranged in line and then blowing a gas or a liquid to the film formation surface behind the resist. Japanese Patent Application KOKAI Publication No. 6-151295 discloses a method of forming a uniform film by splaying a resist to a substrate from a plurality of spray holes formed in a rod. Japanese Patent Application KOKAI Publication No. 7-321001 discloses a method of forming a uniform film by moving a spray head having numeral spray holes for spraying a resist relative to a substrate. All of the coating apparatuses mentioned are directed to the formation of a uniform film by moving output nozzles or spray nozzles arranged laterally in line in a scanning manner along a substrate surface.
To use the chemical agent without waste, a method has been proposed in which a liquid film is formed by supplying a liquid from a nozzle selectively to a film formation region of the substrate. As such a selective film formation method using a liquid supply nozzle, known is a method using an accurate coating nozzle (manufactured by EFD CO., Ltd.) in which output of the liquid can be controlled in an ON/OFF manner.
In the method using the accurate coating nozzle, a liquid 13 is shut out by driving a valve such as a needle 171 or a screw 181, which is provided within a nozzle positioned above an output port 172, as shown in FIGS. 1 and 2.
This system has a problematic phenomenon where particles are generated by friction between the valve and the liquid when the valve is driven, and the particles are delivered to the substrate by being contained in a liquid supplied dropwise onto the substrate when the valve is opened. This system has another problematic phenomenon where pressure applied to the liquid slightly changes immediately after the valve is opened and thereby a pulsation flow occurs. Due to the pulsation flow, the thickness of the formed film changes.
More specifically, if a liquid film is selectively formed on the substrate while controlling output of the liquid by operating the valve arranged before the output port, as described, a problem of liquid-film contamination with the particles comes up. In addition, if the pulsation flow occurs, the liquid film is formed non-uniformly in thickness.
If the substrate has an uneven surface due to various patterns formed thereon, the following problems come up.
As shown in FIG. 3, if constructs 102 are formed on a substrate 101 and the ratio of the depressed portion is different depending on regions of the substrate surface, the thickness of films 103a, 103b, and 103c differs. In this case, the surfaces of the films are not formed uniform. Then, if the structure shown in FIG. 3 is subjected to a reflow processing, the resultant films, for example, insulating films 104a, 104b, and 104c, can be flattened, as shown in FIG. 4A.
However, depending upon the difference in ratio of the depressed portion, the insulating films 104a, 104b, 104c differ in surface level (height). Therefore, when resist patterns 106a-106c are formed on the insulating films 104a-104c with an antireflection film 105 interposed between them and exposed to light, some of them are defocused. The resist patterns 106a-106c obtained after the light exposure have a problem in that line widths thereof drastically vary each other as shown in FIG. 4B.
In brief, as described, the spin-rotation method has a problem in that almost all amount of liquid supplied dropwise on the substrate is wasted. On the other hand, the method of supplying the liquid dropwise onto the substrate has a problem in that the formed liquid film differs in height (level) from the substrate depending upon projections and depressions of the pattern formed on the substrate. In other words, the formed liquid film is non-uniform in thickness measured from the substrate surface.
A first object of the present invention is to provide an apparatus and method for selectively forming a liquid film on a substrate in a uniform thickness while suppressing contamination of the liquid film with impurities. A second object of the present invention is to provide a method of forming a liquid film having a flat surface even on both projections and depressions by coating a liquid on a substrate efficiently without influence from the projections and depressions attributed to patterns formed on the substrate.
The present invention is constituted as described below to attain the first object.
(1) According to the present invention, there is provided an apparatus for forming a film, comprising:
a liquid output portion arranged above a substrate in which a predetermined film formation region and a predetermined non-film-formation region are defined, for continuously outputting a liquid to the substrate in a constant amount;
a moving portion for relatively moving the liquid output portion and the substrate; and
a liquid shut-out portion arranged between the liquid output portion and the substrate, for shutting out supply of the liquid to the non-film-formation region when at least one of the substrate and the liquid output portion is moved and ready to supply the liquid output from the liquid supply portion to the non-film-formation region.
Preferred embodiments of constitution (1) will be described below.
The liquid shut-out portion comprises a liquid suction portion for sucking the liquid output from the liquid output portion, from a side of a liquid flow, and a liquid collection portion for collecting the liquid sucked.
The liquid shut-out portion comprises a gas blow-out portion for blowing out a gas to a side of a liquid output from the liquid output portion and a liquid collection portion arranged so as to sandwich the output liquid with the gas blow-out portion below the gas blow-out portion, for collecting the liquid to which the gas is blown out.
The liquid shut-out portion comprises
a light emitting portion for emitting light for initiating a reaction of a gas generating material;
a light controlling portion for controlling a direction of light emitted from the light emitting portion;
a gas blow-out portion having the gas generating material for generating a gas upon receipt of light controlled by the light controlling portion and blowing out the gas generated to a side of the liquid output from the liquid output portion; and
a liquid collection portion arranged so as to sandwich the output liquid with the gas blow-out portion, for collecting the liquid to which the gas is blown out.
The liquid shut-out portion comprises
a shut-out plate arranged between the liquid output portion and the substrate, for changing a flow of the liquid output form the liquid output portion;
a shut-out plate driving portion for loading and unloading the shut-out plate across the flow of the liquid output from the liquid output portion; and
a liquid collection portion for collecting the liquid whose flowing direction is changed by the shut-out plate.
Furthermore, to the liquid shut-out portion, an image taking section is connected which is arranged in front of a moving direction of the liquid output portion, for taking an image data of the surface of the substrate, and the liquid shut-out portion identifies the non-film-formation region on the basis of the image data taken and a predetermined pattern design data and shuts out supply of the liquid.
(2) According to the present invention, there is provided a method of forming a film comprising the steps of:
outputting a constant amount of a liquid constantly from a liquid output nozzle to a substrate having a predetermined film formation region and a predetermined non-film-formation region defined therein;
supplying the liquid output from the liquid output nozzle to the film formation region on the substrate by relatively moving the liquid output nozzle and the substrate; and
collecting the liquid by changing a direction of a flow of the liquid output from the liquid output nozzle to a direction parallel to a direction of a relative movement of the liquid output nozzle and the substrate by using a liquid shut-out portion arranged between the liquid output nozzle and the substrate and stopped relatively to the liquid output nozzle, and thereby shutting out supply of the liquid to a non-film-formation region of the substrate.
Preferred embodiments of constitution (2) will be described below.
The non-film-formation region is at least one of a region including an alignment mark to be used in alignment in a light exposure step and a region of the substrate to be processed. The xe2x80x9cregion of the substrate to be processedxe2x80x9d is a region to be etched and includes a region such as an outer peripheral portion of a wafer, on which a chip is not formed.
As the liquid, any one of an antireflection material, a resist material, low dielectric material, an insulating material and a wiring material added to a solvent, is used. Note that the material to be added is not limited to the aforementioned materials. As the liquid, a solvent containing an arbitrarily chosen material dissolved therein, such as a metal paste, may be used.
The present invention has the following functions and effects by virtue of the aforementioned constitutions.
The liquid can be shut out by controlling an output amount of the liquid from the nozzle constant and shutting out the output liquid by the liquid shut-out portion provided below the nozzle without generation of particles. Furthermore, it is possible to supply the liquid uniformly to the substrate without generating a pulsation flow by shutting out the liquid by the liquid shut-out portion, immediately before the liquid is shut out, after the shut-out is completed and at the time liquid supply is reinitiated.
No valve is used, so that no pulsation flow is generated in the liquid. As a result, it is possible to form a liquid film having a uniform thickness. Furthermore, the supply of the liquid to the substrate is shut out by bending the supply direction of the liquid in a direction parallel to the moving direction of the apparatus. When the liquid is shut out, the liquid is not scattered out laterally from the moving direction. It is therefore possible to form a liquid film having a uniform thickness.
Since the supply of the liquid onto the substrate is shut out after the liquid is output from the nozzle, no particles are generated and therefore contamination of the liquid film with particles does not take place.
Furthermore, it is possible to reduce an amount of the liquid to be used by shutting out the supply of the liquid from the liquid supply nozzle by the liquid shut-out portion.
The present invention is constituted as described below to attain the second object.
(3) According to the present invention, there is provided a method for forming a film comprising the steps of:
outputting a liquid, which is controlled to be spread in a constant amount on a substrate, continuously to the substrate from a liquid output nozzle;
moving the liquid output nozzle and the substrate, relatively to supply the liquid to a first region on the substrate; and
supplying the liquid to a second region on the substrate by moving the liquid output nozzle and the substrate relatively in such a way that a liquid supplied from the liquid output nozzle and spread on the substrate comes into contact with the liquid which has been supplied and spread in the first region on the substrate.
Preferred embodiments of constitution (3) will be shown below.
When projections and depressions are formed on a surface of the substrate, an amount of the liquid to be supplied onto the substrate is changed depending upon the ratio between the projections and depressions.
The amount of the liquid to be supplied onto the substrate is changed by changing an output amount from the liquid output nozzle.
The amount of the liquid to be supplied onto the substrate is changed by changing a moving speed of the liquid output nozzle relative to the substrate while the amount of the liquid output from the liquid output nozzle is maintained constant.
The output amount is changed by changing a deliver amount from the liquid deliver pump arranged at an upstream side of the liquid output nozzle.
In the step of supplying the liquid to the first region on the substrate, the liquid is supplied in a first supply direction from an edge of an outer periphery of the substrate toward inside while the liquid output nozzle is reciprocally moved in a direction perpendicular to the first supply direction and simultaneously moves in the first supply direction at predetermined pitches when it reaches a point of return.
In the step of supplying the liquid to the second region, the liquid is supplied in a second supply direction from another edge of the periphery of the substrate to the inner portion thereof so as not to overlap the first region while the liquid output nozzle moves reciprocally in a direction perpendicular to the second supply direction and simultaneously moves to the second supply direction at predetermined pitches when it reaches a point of return.
The amount of the liquid to be spread is controlled by controlling at least one selected from an amount of a solid matter contained in the liquid, a viscosity and an output speed of the liquid, and a relative moving speed of the liquid output nozzle and the substrate.
A plurality of liquid output nozzles are arranged in a direction perpendicular to a moving direction of the liquid output nozzle relative to the substrate, for changing amounts of the liquid output nozzles.
The ratio between projections and depressions is determined from pattern design data of the substrate.
The ratio between projections and depressions is determined from an image of a surface of the substrate taken by an image taking section arranged in front of a moving direction of the liquid output nozzle.
As the liquid, any one of a low dielectric material an insulating material, an antireflection material, a resist material, and a wiring material added in a solvent, is used. Note that a raw material to be added is not limited to the aforementioned materials. As the liquid, a solvent containing any arbitrarily chosen material dissolved therein, for example, a metal paste, may be used.
The present invention has the following functions and effects by the aforementioned constitution.
In the present invention, a liquid is supplied from a liquid supply nozzle onto a substrate placed right below the liquid supply nozzle. In this case, the output liquid is held on the substrate to thereby supply only a necessary solid matter to the substrate. Accordingly, it is possible to reduce the cost for materials. In addition, the amount of waste materials is reduced, with the result that adverse effects on the environment can be drastically lowered.
Furthermore, a film having a flat surface can be formed on both depressed portion and projecting portion by changing a relative moving speed of the substrate and the liquid output nozzle, a moving pitch of the nozzle or an output amount of the liquid from the nozzle depending upon the ratio between projections and depressions of the substrate or a desired film thickness.
Furthermore, the present invention can be attained by using a method of shutting out the liquid supplied dropwise. To describe more specifically, the film having a flat surface can be formed both on a depressed portion and a projecting portion by controlling a supply amount of the liquid by intermittently shutting out the liquid to be supplied from the nozzle to the substrate while the substrate and the liquid output nozzle are relatively moved depending upon the ratio between depressions and projections of the substrate or a desired film thickness. More specifically, the surface of the formed film can be flattened by increasing a supply amount of the liquid and spreading the liquid on the substrate surface by reducing the number of shut-out operation in the depressed portion and by decreasing a supply amount and spreading the liquid on the substrate surface by increasing the number of shut-out operation in the projecting portion.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.